The present invention relates generally to the production of container cartons from laminated composite sheet material and more particularly to the production of a film paper laminated composite having a sealed, easily tearable and removable tab portion which may be used to form sealed, liquid-tight cartons with tear out openings.
Lamination of a plastic film material to a paper material has been found to be particularly advantageous where paper products having high strength and abrasion resistant qualities are required. Such laminated composites are particularly desirable in the packaging industry, where artwork may be printed on the interior side of the plastic film to produce a high quality display package. The construction and uee of such laminated composites are described in Peer, U.S. Pat. No. 4,254,173 which is hereby incorporated by reference for all that it discloses.
In producing a laminated composite of the type described in Peer, both the plastic film material and the paper material may be provided in continuous sheets from spools. The paper and the plastic film generally pass over a number of roller type devices where each of the materials are independently stretched out under tension and treated a necessary depending upon the particular end use for the laminated composite. For example the plastic material may be irradiated in conventional processes to increase its strength or improve its printability. In some embodiments the plastic is printed with various graphics and provided with a metalized background over the graphics to enhance the package appearance. The paper may undergo treatment as well such as being electrostatically charged to aid in the bonding process. Either the film material or the paper material or both are treated thereafter with suitable adhesive to provide a bond between the paper and film. To complete the laminating process, the paper and film material are pressed together between opposed rollers to produce a smooth flat composite. Various heating or cooling processes may also be required to ensure proper adhesion of the bonded surfaces, depending on the type of film, paper, add adhesive agent which are being used in such a process. The end product of the process is a laminated composite which may be fed directly to cutting dies or other machines for further processing. The composite may also be collected directly on a separate spool for storage and later processing. Methods for controlling various physical characteristics of the paper web and film web during the lamination process are described in Haake, et al, U.S. Pat. No. 4,572,752; and U.S. patent application Ser. No. 835,234 filed Mar. 3, 1986, now U.S. Pat. No. 4,704,174, for LAMINATING DEVICE WITH PAPER TENSION CONTROL of Roger Allen Thompson et al., which are both hereby incorporated by reference for all that is disclosed therein.
As disclosed in U.S. patent application Ser. No. 517,324, now U.S. Pat. No. 4,691,858 incorporated by reference above, one use of composite material of the type described in Peer, U.S. Pat. No. 4,254,173 is in the production of container cartons such as milk cartons, liquid or powder detergent cartons, dried cereal cartons and other container cartons in which maintaining the container contents in a sealed environment is desirable.
The physical characteristics of composite material, especially composite material having a paper layer sandwiched between a plastic film layer and another moisture barrier layer, are in many ways ideal for container carton construction. The film layer or layers may be extremely thin and yet still function to prevent moisture penetration. The adhesion of the film layer(s) to the paper layer provides a composite material having tear strength and resistance to rupture which is significantly greater than that of conventional paper cartons. Thus composite cartons may be formed using less material than conventional cartons thereby reducing production costs. However, the greater tear resistance of composite cartons may make formation of tear out spouts or other cartons openings relatively difficult. One solution to this problem disclosed in Peer U.S. Pat. No. 4,691,858; incorporated by reference above, is to perforate one layer of plastic film material and a portion of a layer of paper material in a three layer composite having a paper material layer positioned betwee two plastic film layers. A potential problem with this solution is that the carton's ability to prevent liquid penetration may be somewhat compromised through the rupture of one of the nonpermiable plastic layers.
The present invention overcomes this potential problem by providing a method and apparatus for producing a weakened zone in composite material for forming a tear off tab or the like. The weakened zone is formed by perforating the paper layer, and only the paper layer, of a composite material comprising at least one film layer adhered to a paper layer.
Another feature of laminated composite material which makes it desirable for use in container cartons is that an outer film layer may be provided with high quality graphics.
In a high speed laminator of the type described in Haake et al., U.S. Pat. No. 4,572,752, and Thompson et al., U.S. Pat. No. 4,704,174, incorporated by reference above, repeating film graphics patterns are printed on a film web prior to the film web's lamination to a paper web. Ordinarily, the paper web does not contain graphics patterns or other repeating matter which must be placed in registration with the film graphics and thus phasing of the film web to the paper web is not necessary. However, in the method and apparatus of the present invention, a paper web is perforated prior to its lamination to a printed film web, and thus it is necessary to ensure that the perforated portions of the paper web are placed in proper registry with the graphics patterns on the film web. Such registration is complicated by the fact that the film material is relatively extensible and subject to changes in length depending upon operating conditions.
The present invention comprises an apparatus and method for forming a laminated composite having a repeating series of perforated regions in a paper layer which are positioned in registry with a repeating series of graphics patterns on a relatively extensible film layer. The apparatus processes film material and paper material provided in continuous web form to create a continuous web of composite material having such characteristics. The composite material thus formed may be taken up on a composite spool or the like for convenient storage and transportation or may be provided directly to other apparatus for additional process steps leading to the formation of container packages having sealed weakened regions therein which may be ruptured to form an opening for removing the container contents.
The apparatus comprises a paper supply means and a film supply means for supplying a continuous moving web of paper material and a continuous moving web of film material to a laminating means. Prior to entry of the film web and paper web into the laminating means one or both of the surfaces to be bonded is/are coated with an adhesive agent provided by an adhesive supply means. The laminating means apply compressive pressure to the moving paper and film webs by which they are adhesively bonded together to form a moving laminated composite web.
The film material, prior to use in the laminating apparatus, is provided with preprinted (preferably back printed) identical sets of graphics at predetermined spacing intervals hereinafter referred to as repeat length portions of the film web. The repeat length portions are nominally of a constant length but are subject to minor length variations caused by tension changes in the web, ambient temperature change, etc. A predetermined portion of each graphics pattern hereinafter referred to as film "target areas" are designed to be placed in registry with perforated regions of the paper web. Film monitoring means are used to detect the relative position of the film target area with respect to the laminating means. The film monitoring means may comprise photoelectric sensing means for sensing spaced apart printed registration marks on the film.
The paper web prior to entering the laminating means passes through a rotary cutter means which cuts perforated patterns in the paper web at spaced apart intervals. The longitudinal spacing interval of the patterns on the paper web is nominally the same as that of the spacing of target areas on the film web and defines a design repeat length distance.
The present invention provides registry between the target areas on the film web and the patterns on the paper web at the laminating nip by use of a registration means which adjusts the relative position of the perforated pattern "chain" relative the target area "chain" in a phasing mode of operation. "Chain" as used herein will refer to a series of perforated patterns or target areas having equal spacing throughout as opposed to a single perforated pattern or target area. Phasing of the perforated pattern chain with the target area chain is necessary to achieve proper registration at system start up and also to correct out-of-registration conditions caused by discontinuities in the film web such as caused by splicing or by printing errors. Phasing is accomplished through selectively increasing or decreasing the tension in the extensible film web in a selected control portion of the web upstream of the laminating means. The phasing means may comprise a film entry roll means which forms an entry nip which engages the film web upstream of the laminating means. The surface speed of the entry roll means may be selectively varied relative to the surface speed of the laminating roll means whereby the tension in the film web positioned between the laminating cutter roll nip and entry nip may be selectively varied. The tension in the film control portion between the entry nip and the laminating nip is varied relative to a nominal tension provided in an upstream portion of the film web to stretch or shrink a portion of the film web to achieve proper phasing.
A perforated pattern sensing means is provided at a point near the laminating nip whereby the spacing of the perforated patterns relative the laminating nip may be determined. The phasing error between an incoming perforated pattern on the paper web and an incoming target area on the film web is determined by comparison of a signal generated by the pattern sensing means to the film monitoring means signal. This determined phasing error is used to regulate the film entry nip control means whereby the tension in the fllm control zone is varied for a short duration to place the film target areas in proper registry with the perforated patterns.
In the preferred embodiment the various monitoring means signals and input and output signals from the various control means are processed by an electronic processing means which may comprise a microcomputer.
Due to extensibility of the film web, a further problem associated with registration is encountered. That problem is controlling the length of the individual repeat length portions of the film web to ensure that the lengths of the repeat length portions are within close tolerances of the design repeat length value. The film web repeat length distance is controlled by monitoring the actual repeat length distance of each repeat length portion at a position near the laminating means and comparing the measured value to the design repeat length to determine repeat length error. The repeat length error is corrected by stretching or shrinking the film web. The mechanical apparatus for controlling repeat length may be the same as that used for controlling phasing, however different monitoring and data processing functions are performed to achieve repeat length control. The registration control system thus operates in two different control modes: a phasing control mode and a repeat length control mode, which may both use the same mechanical components. The registration control system changes from one operating mode to another depending upon predetermined criteria such as the absolute value of repeat length error and the ratio of repeat length error to phasing error.
Thus a two-layered laminated composite may be formed having spaced apart weakened regions therein. The composite may be collected on a composite takeup means, for temporary storage or may be fed directly into other processing apparatus. In certain preferred embodiments of the invention, a third layer is added to the two-layered composite by laminating a second film layer to the exposed surface of the paper layer or by coating the exposed surface of the paper layer with a moistue barrier material such as "hot melt" plastic or wax. In another embodiment, the paper web is provided with an exterior plastic barrier layer before its opposite side is laminated to the printed film web. Such three-layered composites have a moisture barrier on each exposed surfaces and may be used to provide carton blanks and, subsequently, cartons which have continuous moisture barriers on both the inside surface and the outside surface. The perforated region in the paper layer of such composites may be configured to provide carton tabs or the like which may be easily ruptured and torn away to provide a carton opening such as a pour spout.
Thus, the present invention may also comprise a carton blank having a perforated tab portion which is formed from a unitary sheet of such a three-layered laminated composite material. At least one laminated plastic layer of the carton blank may be back printed with predetermined carton display graphics.
The present invention may also comprise a carton formed from such a carton blank.